Share thisSafety is a complex issue, and in order to fully understand safe use of decontamination agents, it must be examined from many different aspects.
Safety in the laboratory has always been a priority, which is why decontamination technology has advanced over the last ten years to meet the growing needs of lab animal research facilities. Chlorine dioxide gas (CD gas) arrived over ten years ago as the newest commercially available decontamination method. It is still the most recent high-level sterilant on the market, a true gas capable of eliminating all viruses, bacteria, fungi, and their spores; even when hidden beneath, behind, and in-between objects. Some people believe that CD gas is unsafe. Those people are correct. In fact, no method of decontamination is safe, as their sole purpose is to effectively kill organisms; bacterial, viral, human, or otherwise. Each decontaminating agent does, however, have different properties which must be taken into account when looking at safety issues.
Safety Threshold and Typical Use Concentration
One of the first aspects to note is the agent’s 8-hr time weighted average (TWA) allowable exposure limit. CD gas has a low 8-hr TWA concentration of 0.1 ppm according to OSHA. At first glance this looks comparatively worse than the 8-hr TWA for both vapor phase hydrogen peroxide (VPHP) (1.0 ppm) and formaldehyde (0.75 ppm). To get the full perspective on this safety characteristic, however, the typical use concentrations must also be examined. CD gas is typically used at a concentration of 360 ppm, while VPHP has a typical concentration of around 750 ppm, and formaldehyde has a use concentration of around 8000 ppm. Looking at these two values in tandem shows that while CD gas has a lower 8-hr TWA, each decontaminating agent is used at concentrations greatly in excess of their 8-hr TWA. Operating at concentrations significantly higher than the 8-hr TWA, leakage of any decontaminant is dangerous and must be monitored throughout the decontamination cycle.
Leak Detection and Safety
As all methods are used at dangerous levels, the ease and ability to detect leakage is a very valuable aspect regarding how safe a decontaminating agent is. For the two gaseous methods, CD gas and formaldehyde, as well as vapor phase hydrogen peroxide, chemical sensors and personal safety badges are available. Chemical sensors can either be handheld and portable, or fixed to a wall.
Leak detectors can work very well, but will only work in areas where a sensor exists. It is easy for those performing decontaminations to have a chemical sensor with them to ensure their own safety and to check for leakages. It becomes unrealistic to place chemical sensors throughout a facility, or for all individuals working near the space being decontaminated to have them. This is especially true for a busy facility where many people can pass by the space being decontaminated during the duration of the cycle.
The ability to smell the decontaminating agent allows for those not directly associated with the decontamination event to be aware of any unsafe situations. Chlorine dioxide gas has an odor threshold equal to its 8-hr TWA safety level.Most people recognize the smell of chlorine. This can alert workers to potential exposure, whether they are near a chemical sensor or not. Formaldehyde is similar in that it has an odor threshold of 0.8ppm, just above its 8-hr TWA. OSHA states that no odor threshold was determined for hydrogen peroxide. Facility workers must then rely on chemical sensors to gauge if VPHP leakage and exposure levels are above safe levels.